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linux-user: Improve consistency checking in elf headers. 

Validate more fields of the elf header.  Extract those checks
into two common functions to be used in both load_elf_interp
and load_elf_binary.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>
This commit is contained in:
Richard Henderson 2010-07-27 10:25:34 -07:00 committed by Edgar E. Iglesias
parent 682674b841
commit 9058abdd18
1 changed files with 33 additions and 24 deletions
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57
linux-user/elfload.c
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@ -919,6 +919,30 @@ static int elf_core_dump(int, const CPUState *);
#endif /* USE_ELF_CORE_DUMP */
static void load_symbols(struct elfhdr *hdr, int fd, abi_ulong load_bias);
/* Verify the portions of EHDR within E_IDENT for the target.
This can be performed before bswapping the entire header. */
static bool elf_check_ident(struct elfhdr *ehdr)
{
return (ehdr->e_ident[EI_MAG0] == ELFMAG0
&& ehdr->e_ident[EI_MAG1] == ELFMAG1
&& ehdr->e_ident[EI_MAG2] == ELFMAG2
&& ehdr->e_ident[EI_MAG3] == ELFMAG3
&& ehdr->e_ident[EI_CLASS] == ELF_CLASS
&& ehdr->e_ident[EI_DATA] == ELF_DATA
&& ehdr->e_ident[EI_VERSION] == EV_CURRENT);
}
/* Verify the portions of EHDR outside of E_IDENT for the target.
This has to wait until after bswapping the header. */
static bool elf_check_ehdr(struct elfhdr *ehdr)
{
return (elf_check_arch(ehdr->e_machine)
&& ehdr->e_ehsize == sizeof(struct elfhdr)
&& ehdr->e_phentsize == sizeof(struct elf_phdr)
&& ehdr->e_shentsize == sizeof(struct elf_shdr)
&& (ehdr->e_type == ET_EXEC || ehdr->e_type == ET_DYN));
}
/*
* 'copy_elf_strings()' copies argument/envelope strings from user
* memory to free pages in kernel mem. These are in a format ready
@ -1150,33 +1174,16 @@ static abi_ulong load_elf_interp(struct elfhdr * interp_elf_ex,
int i;
bswap_ehdr(interp_elf_ex);
/* First of all, some simple consistency checks */
if ((interp_elf_ex->e_type != ET_EXEC &&
interp_elf_ex->e_type != ET_DYN) ||
!elf_check_arch(interp_elf_ex->e_machine)) {
if (!elf_check_ehdr(interp_elf_ex)) {
return ~((abi_ulong)0UL);
}
/* Now read in all of the header information */
if (sizeof(struct elf_phdr) * interp_elf_ex->e_phnum > TARGET_PAGE_SIZE)
return ~(abi_ulong)0UL;
elf_phdata = (struct elf_phdr *)
malloc(sizeof(struct elf_phdr) * interp_elf_ex->e_phnum);
if (!elf_phdata)
return ~((abi_ulong)0UL);
/*
* If the size of this structure has changed, then punt, since
* we will be doing the wrong thing.
*/
if (interp_elf_ex->e_phentsize != sizeof(struct elf_phdr)) {
free(elf_phdata);
return ~((abi_ulong)0UL);
}
i = interp_elf_ex->e_phnum * sizeof(struct elf_phdr);
if (interp_elf_ex->e_phoff + i <= BPRM_BUF_SIZE) {
memcpy(elf_phdata, bprm_buf + interp_elf_ex->e_phoff, i);
@ -1428,11 +1435,13 @@ int load_elf_binary(struct linux_binprm * bprm, struct target_pt_regs * regs,
load_addr = 0;
load_bias = 0;
elf_ex = *((struct elfhdr *) bprm->buf); /* exec-header */
bswap_ehdr(&elf_ex);
/* First of all, some simple consistency checks */
if ((elf_ex.e_type != ET_EXEC && elf_ex.e_type != ET_DYN) ||
(! elf_check_arch(elf_ex.e_machine))) {
if (!elf_check_ident(&elf_ex)) {
return -ENOEXEC;
}
bswap_ehdr(&elf_ex);
if (!elf_check_ehdr(&elf_ex)) {
return -ENOEXEC;
}
@ -1444,7 +1453,8 @@ int load_elf_binary(struct linux_binprm * bprm, struct target_pt_regs * regs,
}
/* Now read in all of the header information */
elf_phdata = (struct elf_phdr *)malloc(elf_ex.e_phentsize*elf_ex.e_phnum);
elf_phdata = (struct elf_phdr *)
malloc(elf_ex.e_phnum * sizeof(struct elf_phdr));
if (elf_phdata == NULL) {
return -ENOMEM;
}
@ -1549,8 +1559,7 @@ int load_elf_binary(struct linux_binprm * bprm, struct target_pt_regs * regs,
interpreter_type = INTERPRETER_ELF;
}
if (interp_elf_ex.e_ident[0] != 0x7f ||
strncmp((char *)&interp_elf_ex.e_ident[1], "ELF",3) != 0) {
if (!elf_check_ident(&interp_elf_ex)) {
interpreter_type &= ~INTERPRETER_ELF;
}